Children enjoy various drawing and coloring activities using a variety of mediums. Useful in such activities are markers containing inks, crayons and pencils of various colors. However, children would often like to change the color of a mark after they have made the mark. One instance would be the desire to add yellow daisies in a previously colored field of grass and pink flowers. Other consumers including students and various types of workers also require differential marking capability as, for instance, those who routinely highlight clauses of written material of particular relevance. These consumers, as do the children, may change their mind after making a mark, and desire to change the color to set apart certain material.
Changing the color of a mark is not readily done with the typical coloring instruments previously used by consumers, such as those instruments described. In the past, marks were changed by placing the mark of one color over the mark of another color. When performing this using traditional marking pens, the marks produced are often not the desired colors and the tips of the markers get soiled with the other inks, rendering the marker useless. Also, with traditional highlighter inks, the colors tend to bleed together, resulting in undesirable color smears and combinations. Furthermore, oftentimes the use of a second color over the first renders the text illegible.
Therefore, there has been a long felt need for coloring compositions, for use as inks for highlighting, and markers containing such compositions, which produce marks of a first color that can be readily changed into a wide variety of second colors while leaving the highlighted indicia easily visible (i.e., have "read-through" capability). Especially needed is such a group of compositions which may be used in markers without soiling the nib of the second used marking instrument. Optimally, such compositions can be used on different types of paper without fading. In general, coloring compositions are mixtures of a coloring matter dispersed or dissolved in a carrier fluid. If the coloring matter is readily soluble in the carrier fluid it is termed a dye.
In one available marker application, a consumer is able to change a specific initial mark laid down to a second specific color by applying a reducing agent to the first mark yielding a change in color. The marker inks used in these markers are typically prepared by blending a reducing agent (sometimes termed a bleaching agent) or pH-sensitive dye with a dye that is stable in the presence of reducing agent or high pH. For example, German Patent Specification No. 2724820, (hereinafter "the German Patent"), concerns the combining of a chemically stable dye and a chemically unstable dye in an ink formulation. Once a mark using this combination of stable and unstable dyes is laid down, the mark may be overwritten with a clear reducing agent solution, eliminating the color contribution of the unstable dye. The resulting mark of the stable dye, with its characteristic color, remains.
There are several drawbacks to such a marking system. First, there are strict limitations on the number of color changes which may be produced. Specifically, in formulations made according to the German Patent, the particular ink composition may only be changed from a first color to a fixed second color. For example, a green mark may only be changed to a violet color as the inks are described in the practice of the German Patent. In addition, since one of the required pair of markers contains only the reducing agent, that reducing agent marker cannot render a visible mark and may only be used in combination with the base color marker. Once the base color marker is used up, the reducing agent marker is of no use. Or, once the reducing agent marker is used up, the base color marker may only be used for the color which it initially marks with. A further disadvantage of the marking process of the German Patent is that the nib of the reducing agent marker tends to get soiled by picking up the colors of the stable dye in the base coloring composition, thus tainting the color of subsequent marks.
The coloring composition may also optionally include such ingredients as humectants, preservatives, and drying agents. Humectants function to improve freeze/thaw stability and to control drying out of the tip when the coloring composition is used as a marker ink. Preservatives serve the obvious function of preventing spoilage of the coloring composition during the expected shelf life of the product derived therefrom (e.g., marker, ink or dye). Drying agents speed drying of a mark laid down by a marker.
Therefore, an object of the present invention is to provide a coloring composition system which is capable of enhanced multiple color changing abilities, and is especially suitable for highlighting.
An additional object of the present invention is to produce a coloring composition system for use in highlighting which includes at least two different coloring compositions each of which may be used independently or which may be used in combination to provide color changing ability, and each of which preferably leave the highlighted indicia easily visible, either when used alone, or in combination.
A further object of the present invention is to provide a coloring composition system in the form of inks which prevent a nib of a color changing marker from becoming visibly soiled from contacting a base color composition.
These and other objects will become apparent to those skilled in the art to which the invention pertains.